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首页> 外文期刊>Progress in Physical Geography >Modern and past periglacial features in Central Asia and their implication for paleoclimate reconstructions
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Modern and past periglacial features in Central Asia and their implication for paleoclimate reconstructions

机译：中亚近代和过去的冰缘特征及其对古气候重建的启示

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In the continental areas of Central and High Asia, periglacial landform assemblages, sediment structures and processes are mainly influenced and determined by of soil humidity during freeze-thaw cycles. These cryogenic processes result in periglacial landforms such as solifluction, earth hummocks or patterned ground. The distribution of rock glaciers as clear indicators of permafrost is additionally determined by rock fall or moraine debris composed of large boulders (e.g. of granite). Periglacial features were used to reconstruct past climatic conditions, e.g. relict involutions and ice-wedge casts provide evidence for the distribution of former permafrost, say, for the Last Glacial Maximum (LGM). Past temperatures, e.g. mean annual air temperatures, can be estimated from these periglacial features and can be compared with other proxy data, such as glacier fluctuations. Examples from late Holocene solifluction activity in the Altai, Khangai and north-eastern Tibetan Plateau show a different intensity of solifluction processes during the late Holocene and Little Ice Age due to a decrease in temperature and higher soil humidity. The distribution of past permafrost in some regions is still a matter of debate because of different interpretations of sediment structures: sometimes features described as ice-wedge casts may be caused by roots or desiccation cracks due to drying of clay rich sediments. Seismically deformed unconsolidated deposits (seismites) can also be misinterpreted as periglacial involutions. The lack of certain landform assemblages and sediment structures does not necessarily mean that the area had no permafrost. Moisture conditions can also determine the periglacial landform generation to a large degree. They can be ordered in Central Asia as follows (from highest moisture availability to lowest): solifluction; rock glacier; permafrost involutions; ice-wedge casts; sand-wedge casts.
机译：在中亚和高亚洲的大陆地区，冰冻融化过程中，冰缘地貌组合，沉积物结构和过程主要受土壤湿度的影响和确定。这些低温过程导致了冰川边缘地貌，例如固溶，土丘或图案化的地面。岩石冰川的分布是永久冻土的明确指示，另外还取决于岩石崩落或由大石块（例如花岗岩）组成的冰ora碎片。沿冰缘特征被用来重建过去的气候条件，例如遗迹的对合和楔形的冰块为前多年冻土的分布提供了证据，例如，最后一次冰期最大值（LGM）。过去的温度，例如这些冰川期特征可以估算年平均气温，并且可以与其他代理数据（如冰川波动）进行比较。来自阿尔泰，坎盖和青藏高原东北部的全新世晚期固溶活动的例子表明，由于温度降低和土壤湿度升高，全新世晚期和小冰期的固溶作用强度有所不同。由于对沉积物结构的不同解释，过去多年冻土在某些地区的分布仍是一个有争议的问题：有时描述为冰楔形铸件的特征可能是由于干燥富含粘土的沉积物而引起的根部或干燥裂缝所致。地震变形的未固结沉积物（地震岩）也可能被误解为冰缘复合。缺乏某些地貌组合和沉积物结构并不一定意味着该地区没有多年冻土层。湿度条件也可以在很大程度上决定冰缘地貌的产生。可以按以下顺序从中亚订购（从最高水分供应到最低水分）：岩石冰川多年冻土卷入;冰楔型;砂楔铸件。

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